2. Field of the Invention
The present invention relates to a method for producing hydrocarbons having two carbon atoms (hereinafter referred to as C.sub.2 hydrocarbons) such as ethane, ethylene or acetylene by dihydrogenative coupling of methane.
2. Discussion of Background
A C.sub.2 hydrocarbon, particularly ethylene, is the most important substance used as a base material for petrochemical processes presently available, and a number of products are produced therefrom. As is well known, at present, ethylene is produced in a large amount from petroleum as the starting material. Recently, an attention has been drawn to utilization of natural gas as the starting material for chemical industry, in connection with a problem of exhaustion of petroleum resources. There have been attempts by various sectors to change the starting material and to produce ethylene by catalytically oxidizing and dehydrating natural gas i.e. methane. If ethylene can efficiently be synthesized from methane as the main component of natural gas, it can be used directly to the petrochemical processes presently available, whereby the petroleum resources can be saved. Thus, the impact to the chemical industry will be substantial.
With such an object, a method has been studied wherein a gas mixture of methane and oxygen is used as the starting material, and methane is subjected to oxidative coupling by means of various catalysts or without using a catalyst to produce C.sub.2 hydrocarbons. For example, an oxidative coupling method by Epson Company is known (Japanese Unexamined Patent Publication No. 01607/1985).
The oxidative coupling reaction as disclosed in the above publication is an exothermic reaction and thus has a merit that the reaction temperature is relatively low. However, it has demerits that the yield of the C.sub.2 hydrocarbons and the selectivity for ethylene are low, and water produced as a by-product has no substantial value.